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9. O2 SENSOR SIGNAL CIRCUIT With a scan tool, monitor the O2 Sensor voltage with the jumper wire removed. NOTE: The scan tool will display all O2 Sensor voltage readings at approximately 5.0 volts when one O2 NOTE: The scan tool will display one O2 Sensor voltage close to zero and the others will read lower than Check the O2 Sensor signal circuit for a short to ground, open circuit, short to voltage, or high resistance. Were any problems found? Yes >> Repair as necessary. Perform the PCM Verification Test Ver. 1 (Refer to 9 - ENGINE - DIAGNOSIS AND TESTING). No >> Go to 10 10. O2 SENSOR RETURN CIRCUIT Check the O2 Sensor return circuit for a short to ground, open circuit, short to voltage or high resistance. Were any problems found? Yes >> Repair as necessary. Perform the PCM Verification Test Ver. 1 (Refer to 9 - ENGINE - DIAGNOSIS AND TESTING). No >> Go to 13 11. RESTRICTED FUEL SUPPLY LINE WARNING: The fuel system is under a constant pressure, even with the engine off. Before testing or ser- Install special 5/16 fuel line adapter tool #6539 between disconnected fuel line and the fuel pump module. Attach a fuel pressure test gauge to the T fitting on tool #6539. Ignition on, engine not running. With a scan tool, actuate the Fuel Pump Relay control and observe the fuel pressure gauge. NOTE: Fuel pressure specification is 407 KPa +/- 34 KPa (59 psi +/- 5 psi). CAUTION: Stop all actuation tests before proceeding. Is the fuel pressure within specification? Yes >> Repair or replace fuel supply line as necessary. Perform the PCM Verification Test Ver. 1 (Refer to 9 - ENGINE - DIAGNOSIS AND TESTING). No >> Go to 12 12. FUEL PUMP INLET STRAINER Turn the ignition off. WARNING: The fuel system is under a constant pressure even with the engine off. Before testing or ser- Is the Fuel Inlet Strainer plugged? Yes >> Replace the Fuel Pump Inlet Strainer. Perform the PCM Verification Test Ver. 1 (Refer to 9 - ENGINE - DIAGNOSIS AND TESTING). No >> Replace the Fuel Pump Module. Perform the PCM Verification Test Ver. 1 (Refer to 9 - ENGINE - DIAGNOSIS AND TESTING). PM ENGINE ELECTRICAL DIAGNOSTICS - GPEC 9 - 171 |